1. Field of the Invention
The present invention concerns a method for sending sets of data on an uplink dedicated transport channel made of successive sub-frames from a mobile station to a base station of wireless communication network
2. Discussion of the Background
In a wireless communication system, the data are transmitted on up-link dedicated transport channels (DCH) from the mobile station to the base station.
In UMTS standard, the 3 GPP (3rd Generation Partnership Project) is studying how to enhance uplink Dedicated Transport Channel. The goal and assumption of the study are disclosed in technical report TR 25.896 version 0.3.0 “Uplink Enhancements for Dedicated Transport Channels”.
Since the use of IP based services becomes more important, there is an increasing demand to improve the coverage and throughput as well as to reduce the delay of the uplink. Applications that could benefit from an enhanced uplink may include services like video-clips, multimedia, e-mail, telematics, gaming, video-streaming etc.
Scheduling of mobile station transmissions is considered by 3 GPP to support Enhanced Uplink Dedicated Transport Channel.
In TR 25.896 version 0.3.0, two approaches are mentioned: rate scheduling and time scheduling. Moreover, a hybrid scheme of these approaches is considered.
In rate scheduling, uplink transmissions are executed in parallel and each transmission rate is controlled. Therefore, transmission rate should be low enough. It means that the transmission power of mobile stations is restricted.
In time scheduling, the number of mobile stations that are allowed to transmit are restricted at any given time. The transmission power of mobile stations is also restricted in case of time scheduling, even if it is higher than in case of rate scheduling for avoiding to impact on other channels.
In section 7.2.2 of TR 25.896 version 0.3.0, it is mentioned that multiple stop-and-wait (SAW) hybrid Automatic Repeat Request (ARQ) process can be used for achieving the transmission of data.
In single SAW ARQ process, after a mobile station transmits a data packet, it never transmits a next data packet until receiving a response (ACK or NACK) for the packet transmitted. Therefore, there is time duration in which nothing is transmitted.
Multiple SAW ARQ overcomes this inefficient use. In this multiple SAW ARQ, several SAW ARQ processes operate in parallel.
When the scheduling is done, noise rise (interference level) should be considered. The noise level (mainly interference) must be lower than certain level to keep a high quality defined by the bit error rate, the block error rate and so on.
When a channel resource is assigned to a new mobile station, the transmission power of any given mobile station interferes with other mobile stations as noise. This phenomenon should be taken into account for scheduling. Also, permitted transmission power (equal to permitted transmission rate) to a new mobile station is decided based on remaining quantity up to maximum permitted noise rise.
In 3 GPP discussion, the characteristic of SAW ARQ process is not considered for the scheduling at the moment. When the mobile station uses only one SAW ARQ process, there is no transmission during the period waiting a response. For instance, if the transmission timing from several mobile stations is the same, the noise rise becomes high in specific sub-frames and does not exist in other sub-frames.
Moreover, the rate scheduling needs to set a margin when it decides maximum transmission power of each mobile station as considering the case that all mobile stations transmit at the same time.